The fiftieth anniversary of the liquid crystal display

ABSTRACT

A record is given of the special meeting organised by the UK&I Chapter of the Society of Information Display held at the Royal Academy of Engineering in London, to celebrate the 50th anniversary of the RCA announcement of the first Liquid Crystal Display on 28th May 1968. Coming exactly eighty years after the report of the first liquid crystal materials, this announcement sparked interest across the globe, and particularly in the UK, Switzerland and Japan. Presentations of the early LCD history from Hilsum, Schadt and Raynes give insights into both the science and also the process of invention itself. These early contributors are followed by a view from the USA from Bos and representation from the companies Sharp and Merck that helped shape the success of these fascinating and useful materials. Also reviewed are talks on the use of organic semiconductors to drive plastic LCD by Sirringhaus, reflective LCD of Folium Optics, retail signage of Displaydata, as well as a look to the future from LCD competitors from Bodle (Phase Change Material displays) and BOE (OLED).     

Structural study of PbO-MoO3-P2O5 glasses by Raman and NMR spectroscopy

Glasses in the ternary system PbO-MoO₃-P₂O₅ were prepared in three compositional series (100 − x)[0.5PbO-0.5P₂O₅]-xMoO₃ (A), 50PbO-yMoO₃-(50 − y)P₂O₅ (B) and (50 − z)PbO-xMoO₃-50P₂O₅ (C) and their structure was studied by Raman and ³¹P NMR spectroscopies. In the compositional series (100 − x)[0.5PbO-0.5P₂O₅]-xMoO₃ homogeneous glasses were prepared in the concentration region of 0-70 mol% MoO₃. Their glass transition temperature increases with increasing MoO₃ content having a maximum at x = 50 mol% MoO₃. ³¹P MAS NMR spectra reveal that in the glass series (A) the incorporation of MoO₃ results in the shortening of phosphate chains and gradual transformation Q² units into Q² and Q⁰ units, prevailing in glasses with a high MoO₃ content. Octahedral structural units MoO₆ dominate in most glass compositions and they are present also in the structure of Pb(MoO₂)₂(PO₄)₂ compound corresponding to the glass composition 50Pb(PO₃)₂-50MoO₃. The analysis of Raman spectra of glasses of the (B) series with a high MoO₃ content showed the transformation of octahedral MoO₆ units into tetrahedral MoO₄ units.     

Structural change of liquid Si15Te85 and Si20Te80 with temperature: Ab initio molecular dynamics simulations

Using ab initio molecular dynamics simulations, the structural and electronic properties of liquid Si₁₅Te₈₅ and Si₂₀Te₈₀ at two temperatures were studied respectively. Compared with available experimental data, the calculated structure factors are acceptable. From symmetry arguments, the calculated partial bond-angle distribution functions suggest that with increasing temperature the extensive tetrahedral network structures persist longer in liquid Si₂₀Te₈₀ than those do in liquid Si₁₅Te₈₅. Our results indicate that the local tetrahedral structure around Si atoms and the Peierls-like distorted local atomic structure around Te atoms both play important roles in the structural change of liquid Si₂₀Te₈₀ and Si₁₅Te₈₅, which also suggest that the mechanisms of the structural change upon cooling in liquid Si₂₀Te₈₀ and Si₁₅Te₈₅ are of no essential difference. The results of DOS and LDOS indicate that the variation of the dip in DOS at E_F mainly results from the change of Te p orbitals.     

Solid state H NMR study of molecular dynamics and domain sizes in PBT with the fullerene derivates: Decylamine-C60 and tetracyanoethylene oxide-C60

The solid-state ¹H NMR on-resonance and off-resonance techniques have been performed to study molecular dynamics and domain sizes in heterogenous nanocomposites based on poly(butylene terephthalate) and nanoparticles C₆₀ modified by n-decylamine (DA) or tetracyanoethylene oxide (TCNEO), respectively. The spin-lattice off-resonance relaxation times in the rotating frame T_1ρ^off as well as the second moment M₂ of the absorption line were analysed as a function of temperature. To determine the size of heterogeneities and characterize the morphology of the nanocomposites, the ¹H NMR spin-diffusion experiment designed by Goldman-Shen [1,2] was performed. The results from the measurements allow us to investigate the spin-diffusion phenomenon and relaxation behavior of the new nanocomposites.     

The effect of position of octadecyloxy tail on the formation of liquid crystal with chalconyl-ester and chalconyl-vinyl ester series: Comparison with corresponding linkage group

Understanding of the electronic structures is indispensable for complete elucidation of the charge carrier behaviors in organic semiconductors. Although recent progress enabling accurate photoemission demonstrations of organic single crystals has greatly promoted such understanding, it had been achieved merely on partially oxidized surfaces by exposure to ambient conditions. In this study, we successfully prepared an oxide-free surface of the pentacene single crystal (PnSC) by cleavage in vacuum. X-ray and ultraviolet photoelectron spectroscopy measurements on the PnSC clean surface revealed improved energetic homogeneity of the C1s level and highest-occupied state in comparison to those of the partially oxidized surface.     

UV spectral characterization of a smectic-C liquid crystal: Theoretical support to the experiment

In the present article, UV spectral characterization of a smectic-C liquid crystal 4,4′-bis(n-alkoxy)azoxybenzene (n = 14) (C₄₀H₆₆N₂O₃) has been carried out. Structure of the molecule has been optimized using the Density functional B3LYP with 6-31+G (d) basis set using crystallographic geometry as input. The absorption spectra have been estimated in the UV region by employing the DFT method, semiempirical CNDO/S and INDO/S parameterizations. The oscillator strength (f) and vertical transition energy (E_V) have been reported corresponding to absorption wavelength (λ_max). These values have been compared with the experimental value reported in the literature to offer theoretical support to the experimental value. Further, some electrochemical properties have been reported for the molecule.     

Structural determination by X-Ray diffraction and 183W NMR spectroscopy of mono substituted hexatungstates [(n-C4H9)4N]3MW5O19 (M = Nb, V)

The tetrabutylammonium salt of mononiobotungstate [(n-C₄H₉)₄N]₃NbW₅O₁₉ (1) and the tetrabutylammonium salt of monovanadotungstate [(n-C₄H₉)₄N]₃VW₅O₁₉ (2) are isotypes; both crystallize in the monoclinic system, space group C2/c (N° 15) with Z=8. The cell parameters for 1 are a=30.4038(8) ?, b=18.5948(8) ?, c=27.3330(3) ?, β=112.4555(6)°, V=14281.1(7) ?³ and the final reliability factors are R=0.043 and R _w=0.047 for 5801 reflections. The cell parameters for 2 are a=30.096(8) ?, b=18.373(3) ?, c= 27.201(6) ?, β=112.402(14)°, V=13906(5) ?³ and the final reliability factors are R=0.048 and R _w=0.054 for 6122 reflections. Both anions, [NbW₅O_19] ³⁻ and [VW₅O_19] ³⁻ exhibit the Lindqvist structure of the parent hexatungstate anion. The six metal positions are disordered and for each metal site the occupation factor is close to 1/6 M (M=Nb, V) and 5/6 W. Furthermore the two compounds were characterized by IR in the solid state, and ¹⁸³W solution NMR. The ¹⁸³W spectrum of [NbW₅O_19] ³⁻ presents two resonances with relative intensities 4:1 in agreement with the C_4v symmetry of the anion.     

Laser heated pedestal growth of orthorhombic SrHfO3 single crystal fiber

SrHfO₃ single crystal fibers were grown by the laser heated pedestal growth technique. These fibers have orthorhombic symmetry with lattice parameters of a=5.773(1) Å, b=5.764(3) Å, c=8.157(2) Å at 300 K.     

Laser wavelength effect on structural and optical properties of Cd34Se66 nanocrystalline thin film

Cadmium Selenide (Cd₃₄Se₆₆) thin films are deposited on a glass substrate using the thermal evaporation method at room temperature. The Cd₃₄Se₆₆ films are characterized using XRD. The crystallite size of the film is calculated from XRD data, which is found as 29.61 nm as-deposited. It is also found that crystallite size of Cd₃₄Se₆₆ changed after irradiation with N₂ and Nd:YAG laser. The changes in the optical properties of the films after irradiation with N₂ laser and Nd:YAG laser are also studied in the wavelength range of 300-700 nm and it is found that the optical band gap of the Cd₃₄Se₆₆ films changed after laser irradiation.     

On the solidification of the Fe50Cr15Mo14C15B6 bulk-amorphized alloy

Investigations of the effect of the initial liquid phase state on the processes of solidification in Fe₅₀Cr₁₅Mo₁₄C₁₅B₆ bulk-amorphized melts have been carried out by differential thermal analysis, X-ray structural analysis, metallography and viscosimetry. The anomalies caused by changing the relation of the atom microgroups of boride and carbide types have been discovered for the first time in polytherms of the melt viscosity in the vicinity of 1653 K and 1793 K. The structural changes observed in the liquid phase result in anomalies in the Fe₅₀Cr₁₅Mo₁₄C₁₅B₆ melt supercooling behaviour and a change in the crystallization mechanism. Structural transformation temperatures, can be considered to be an additional factor in the search for promising alloys with optimized glass forming abilities and enhanced service properties.     

Synthesis, growth and characterization of a new laser upconversion crystal Ba2ErCl7

A modified method to synthesize the new laser upconversion material Ba₂ErCl₇ using Er₂O₃, BaCl₂ 2H₂O and NH₄CI is reported for the first time in this paper. Single crystals up to 5–8mm in diameter and 10–20 mm in length have been grown by Czochralski method. The transmittance spectra of Ba₂ErCl₇ single crystal has first been measured by using an HITACHI U-3500 spectrophotometer. There are three intense absorption peaks ⁴I_9/2⁴I_11/2 and ⁴I_13/2 in the infrared range which can be excited by 803nm, 980nm and 1.5μm laser diodes (LDs), respectively. The cut-off wavelength of the crystal is 230mn. Intense green luminescence can be observed when the crystal is pumped by a ED at 803nm. The formation of the defects is also discussed.     

Growth and optical properties of self-frequency-doubling laser crystal Yb:LuAl3(BO3)4

Single crystal of Yb:LuAl₃(BO₃)₄(Yb:LuAB) was grown by the flux method for the first time. The cell parameters of the grown crystal were estimated by X-ray diffraction analysis. The result indicates the symmetry of trigonal space group R32, with lattice parameters a=b=9.26372 Å, c=7.21405 Å, V=536.14 Å³, and Z=4. The absorption and emission spectra of Yb:LuAB crystal at room temperature has also been studied. The fluorescence lifetime for Yb:LuAB crystal is about 1.48 ms. The heat capacity was measured from 25 to 500 °C. Its second harmonic generation efficiency in LuAl₃(BO₃)₄ crystal is 3–4 times that of KDP crystal. These results show that Yb:LuAB crystal would be a potential self-frequency-doubling laser crystal.     

Growth of NaBi(WO4)2 crystal by modified-Bridgman method

NaBi(WO₄)₂ (NBW) crystals have been grown for the first time by modified-Bridgman method. Influences of some factors on the crystal growth process are discussed. X-ray powder diffraction experiments show that the unit cell parameters of NBW crystal are a=b=0.5284 nm, c=1.1517 nm, and V=0.3215 nm³. The differential thermal analysis shows that the NBW crystal melts at 923°C.     

Growth and self-frequency doubling laser output of Nd : Ca4Gd0.275Y0.725O(BO3)3 crystal

In this letter, Nd : Ca₄Gd_0.275Y_0.725O(BO₃)₃ (Nd : GdYCOB) single crystal with good optical quality and large size has been grown by the Czochralski method. The absorption and fluorescence spectra have been measured. The self-frequency doubling (SFD) laser output of Nd : GdYCOB at 0.53 μm has been demonstrated when a Nd : GdYCOB crystal sample with dimensions of 3 mm×3 mm×7 mm (the phase-matched angle is θ=78.8°, Φ=90°) is pumped by a cw Ti : sapphire laser.     

Influence of Y2O3 on structural and optical properties of SiO2-BaO-ZnO-xB2O3-(10−x) Y2O3 glasses and glass ceramics

SiO₂-BaO-ZnO-xB₂O₃-(10−x) Y₂O₃, (0 ≤ x ≤ 10) glasses are synthesized. The effect of Y₂O₃ on the structural and optical properties of glasses has been investigated using different characterization techniques. The results are discussed in light of non-bridging oxygens (NBO), optical basicity and heat-treatment of glasses. The band gap has been calculated for as cast and heat-treated glasses. The band gap energy is found to decrease with the increasing content of Y₂O₃ in the glasses and heat-treatment. The presence of the crystalline phase in the glass matrix showed remarkable effect on band gap which decreases to semiconducting range.     

Characterization of the disordered phosphate network in CaO-P2O5 glasses by P solid-state NMR and Raman spectroscopies

In this study, the disordered network of calcium phosphate glasses is investigated by Raman scattering and ³¹P magic angle spinning (MAS) solid-state NMR spectroscopies. The use of both spectroscopies in a combined approach allows drawing a detailed understanding of the structure of these glasses. The P―O―P connectivity between successive PO₄ tetrahedra is probed using through-bond double quantum-single quantum (DQ-SQ) and triple quantum-single quantum (TQ-SQ) MAS NMR correlation experiments. Over the broad range of glass compositions studied here, two very different phosphate network topologies are encountered. The results obtained for the polyphosphate compositional range (above 50 mol% Ca) allow determining the phosphate chain-length distribution in the glass as a function of the modifier cation content. For the ultraphosphate region (below 50 mol% Ca), the network topology undergoes a sudden change close to 39 mol% Ca which can be interpreted in terms of a rigidity transition.     

Multinuclear NMR study of phosphosilicate gels derived from POCl3 and Si(OC2H5)4

Solid state ¹H, ²⁹Si and ³¹P MAS NMR have been used to investigate the microstructure of phosphosilicate gels prepared by a modified sol-gel method involving hydrolysis of silicon precursors in a solely aqueous environment at 50 °C. Gels with molar compositions 5, 10, 20 and 30 mol% P₂O₅ in P₂O₅-SiO₂ were studied. After drying to 400 °C the gels have very similar structures formed by a siloxane framework containing silanol groups and trapped molecules of orthophosphoric acid together with a very small amount, of pyrophosphoric acid. Unlike the gel samples previously synthesized by the hydrolysis of the silicon precursor in alcoholic solution at room temperature, the co-polymerization of phosphorus and silicon is much reduced. Although co-polymerization increases with phosphorus content, it still represents less than 50% of the phosphorus in the 30 mol% P₂O₅ gel. Furthermore there is no evidence for six-coordinated silicon in the glassy matrix.